In a power module composed of a plurality of semiconductor chips including a power device, it is conventionally a significant problem to diffuse heat of a semiconductor device generated through power loss of the power device (for example, see Document 1 (Power Electronics Handbook (R & D Planning), edited by Koji Imai (p. 602)). Therefore, a conventional semiconductor apparatus is designed, for cooling a power device and keeping its temperature below the safety operating temperature, to place the power device in contact with the package base material so that heat generated in the power device can be released through a package base material through heat conduction. Accordingly, in the case where a power module is constructed by using a plurality of semiconductor chips, it is necessary to make every semiconductor device in contact with a package base material.
FIG. 11 is a cross-sectional view of a conventional semiconductor power module composed of three Si power devices. As shown in FIG. 11, the conventional semiconductor power module includes a base material 101 provided with a fin 101a on its back face for releasing heat, Si chips 102, 103 and 104 corresponding to the three Si power devices secured on the upper face of the base material 101 through soldering, and bonding wires 105 for electrically connecting the Si chips 102, 103 and 104 to one another. Owing to this structure, heat generated in the Si chips 102, 103 and 104 can be efficiently diffused to the base material 101 through the heat conduction, and therefore, the temperatures of the Si chips 102, 103 and 104 corresponding to the power devices can be suppressed to 150° C. or less, that is, their temperature assurance range.